1. Alice and Bob want to communicate over an insecure medium. Design, on the basis of a shared secret key KAB, a protocol, which enables Alice and Bob to authenticate each other. Assume that the shared secret key KAB is known in advance to both partners. b.) What are the disadvantages related to the use of a shared secret key? 2. Alice and Bob want to communicate over an insecure medium. Design, on the basis of a shared secret key KAB, a protocol, which enables Alice and Bob to authenticate each other. Assume that the shared secret key KAB is not known in advance to both partners